Optical method and apparatus for inspecting documents

Abstract

Document inspection apparatus comprises a document transport system ( 1 ) for transporting documents through a detector station ( 6 ). A linear array of separately activatable light sources ( 14, 15 ) at the detector ( 12 ) receives light transmitted through or reflected by any of the illuminated portions of the document and generates a corresponding output signal. A control system ( 9 ) sequentially activates the light sources and monitors the output signals from the detector.

1 . A method of obtaining information about a document, the method comprising transporting the document along a transport path; sequentially illuminating, with light having the same wavelength, a plurality of portions of the document along a line transverse to the transport direction; and detecting, using a common detector, light that has been transmitted through or reflected by the document so as to determine the response of the respective, different portions of the document to the illumination.  
     
     
         2 . A method according to  claim 1 , wherein the illumination wavelength is outside the visible range.  
     
     
         3 . A method according to  claim 2 , wherein the illumination wavelength is in the infrared range.  
     
     
         4 . A method according to any of the preceding claims, wherein one plurality of the portions is illuminated with a different wavelength from another plurality of portions.  
     
     
         5 . A method according to any of the preceding claims, further comprising storing the response in a memory.  
     
     
         6 . A method according to any of the preceding claims, further comprising repeating the illumination and detecting steps so as to determine the response of more than one array of portions.  
     
     
         7 . A method according to any of the preceding claims, wherein the portions extend up to an edge of the document.  
     
     
         8 . A method according to any of  claims 1  to  6 , wherein the portions extend across a central region of the document.  
     
     
         9 . A method according to any of  claims 1  to  6 , wherein the portions extend across the full dimension of the document transverse to the transport direction.  
     
     
         10 . A method according to any of the preceding claims, wherein the portions extend along a line substantially orthogonal to the transport direction.  
     
     
         11 . A method of handling documents comprising obtaining information about each document using a method according to any of  claims 1  to  10 ; comparing the obtained information with predetermined information; and processing the document thereafter in accordance with the result of the comparison.  
     
     
         12 . A method of handling documents of value such as banknotes according to  claim 11 , wherein the comparison step determines one or both of the value and authenticity of the document.  
     
     
         13 . Document inspection apparatus comprising a document transport system for transporting documents through a detector station; a linear array of separately activatable light sources at the detector station for illuminating corresponding portions of the document with light having the same wavelength; a common detector for receiving light transmitted through or reflected by any of the illuminated portions of the document and for generating a corresponding output signal; and a control system for sequentially activating the light sources and monitoring the output signals from the detector.  
     
     
         14 . Apparatus according to  claim 13 , further comprising one or more further linear arrays of separately activatable light sources at the detector station for illuminating corresponding portions of a document, each array cooperating with a respective detector common to that array for receiving light transmitted through or reflected by any of the portions of the document illuminated by that array.  
     
     
         15 . Apparatus according to  claim 13  or  claim 14 , wherein the light sources comprise light emitting diodes.  
     
     
         16 . Apparatus according to any of  claims 13  to  15 , wherein the or each detector comprises a photodiode.  
     
     
         17 . Apparatus according to any of  claims 13  to  16 , wherein the light sources generate wavelengths outside the visible range.  
     
     
         18 . Apparatus according to  claim 17 , wherein the light sources generate wavelengths in the infrared range.  
     
     
         19 . Apparatus according to any of  claims 13  to  18 , wherein one plurality of the light sources generates illumination at a different wavelength from another plurality of light sources.  
     
     
         20 . Document handling apparatus comprising document inspection apparatus according to any of  claims 13  to  19 ; a store for storing predetermined data relating to the documents, wherein the control system is adapted to compare output signals from the or each detector with corresponding prestored data in the store and to issue appropriate control signals determining the further processing of the documents.  
     
     
         21 . Apparatus according to  claim 20 , wherein the predetermined data relates to the value and/or authenticity of documents of value.